The present invention relates broadly to the art of transporting and selectively sorting minute particles, such as fine powders, for example. It finds particular application in conjunction with the handling and processing of pharmaceutical and non-pharmaceutical ingredients and compounds, and will be described herein with particular reference thereto. However, it is to be specifically understood that the present invention can be used in a wide range of other applications, and is equally applicable in a variety of other industries, such as biotechnology, chemical production and processing and other material handling and processing applications, for example. As such, the present invention is not intended to be in any way limited or constrained to uses and/or applications within the pharmaceutical industry.
In the pharmaceutical industry, as well as other industries, there is a need for bulk quantities of uniformly sized particles. Such particles are commonly in the form of dry powders, and typically possess an electrostatic charge. In the production of medicines, for example, the uniformly sized particles are important for both intermediate processing during manufacturing, for producing products having the proper dosage and for timed-release of medication during usage. Unfortunately, bulk quantities of ingredients and compounds often include particles in a wide variety of sizes. For example, particles having a dimension ranging from about 1.0 μm to about 100 μm are common. As such, it is commonly desirable to separate or sort the particles into two or more groups according to size.
Typically, the sorting of bulk quantities of particles is accomplished using mechanical devices, such as sieves, screens and/or other sizing machines. There are numerous disadvantages that are commonly associated with the use of such equipment. One such disadvantage is that commonly associated with mechanical equipment in general. That is, mechanical devices have moving parts that require maintenance and repair. This causes losses due to decreased production, as well as the direct costs of such maintenance and repairs.
Another disadvantage of mechanical sorting devices is that the same can create fines or fragments of particles. These can cause screens in mechanical sorting devices to become clogged, and can also negatively effect the quality and consistency of the sorted particles.
Still another disadvantage of traditional mechanical devices is that conveyors or other similar material moving devices are required to move the bulk particles from one sorting machine to the next, as the particles become more and more separated. This adds additional costs and complexities to the system.
Devices suitable for transporting bulk quantities of particles, such as toner for copy machines, for example, have been developed that use electrostatic traveling waves to move the particles. While these devices overcome some of the disadvantages of mechanical conveyors, devices using electrostatic traveling waves have to date presented shortcomings that have limited their utility. One shortcoming is that for image development, these devices often require particles having specific characteristics, such as a certain electrical charge magnitude, polarity or other property, for example.
Other traveling wave arrangements are based on the use of dipolar forces. One disadvantage of such arrangements is that these devices commonly operate using very high voltages, such as about 2000 V, operate at very high frequencies, such as about 10–100 Mhz, and require very fine line pitches between conductors, such as about 10 μm or less, for example. Additionally, these types of traveling wave devices do nothing to overcome the disadvantages of mechanical sorting devices.